This invention relates to a connector used for connecting an extension electronic circuit board having a memory device to a motherboard in a computer or similar other purposes, and more particularly to an operation assuring structure of an electronic circuit board in a connector for said electronic circuit board.
The electronic circuit board is connected for extension to the motherboard through a connector mounted on the motherboard. Accordingly, the electronic circuit board is provided on one end portion thereof with an insert plate portion to be inserted into a receiving port of the connector. The signal electrode pads and ground electrode pads arranged on the surface of both sides of the insert plate portion at small pitches are pressure contacted with the signal contacts and the grounding contacts held in the receiving port for the connector, and the signal contact and the grounding contact are contacted with a signal line and a grounding line of the mother board.
In order to enhance an easy transmission of a high speed signal (high frequency signal) to a signal line by means of circuit designing, the electronic circuit board and the mother board (electronic circuit motherboard built in a computer) is designed such that the impedance of the signal line will be constant (in general, 50 .OMEGA.). For example, to provide a grounding line in the vicinity of the signal line is also one of the specific examples thereof.
However, in the connector for the electronic circuit board, since the signal contacts are arranged in array at small pitches, and they are pressure contacted with the signal electrode pads arranged in array at small pitches on the surface of one side of the electronic circuit board, a problem of stroke occurs between the signal contacts forming an input end or an output end of the signal line, or the impedance with respect to the high frequency signal of the signal contact cannot be brought into a correct value, and as a result, a problem of delay in transmission speed will occur when a high speed signal is transmitted.
In order to solve the above problems, the present inventors gave a thought to a process for bringing the grounding contact into contact with the grounding electrode pad between the signal contacts which are pressure contacted with the signal electrode pad by disposing the grounding electrode pads between the signal electrode pads. However, in such a construction, it is required to provide a new grounding electrode pad between the signal electrode pads which are arranged at small pitches, and therefore, presuming the arrangement pitches for the signal electrode pads are, for example, 1.0 mm each, the pitches between the signal electrode pad and the grounding electrode pad becomes 0.5 mm. As a result, manufacturing difficulty is encountered. In addition, it becomes increasingly difficult to correctly position the signal electrode pad and the grounding electrode pad, and the signal contact and the grounding contact so that they will be in correct corresponding relation to each other.
Moreover, according to the above process, since all the signal and grounding contacts are pressure contacted with all the signal and grounding electrode pads, respectively, the total number of cores to be subjected to pressure contact becomes about twice and the withdrawing force with respect to the connector of the electronic circuit board is overly increased.
The concept of the present invention came across the present inventors' mind based on the above finding.